1. Field of the Invention
The present invention relates to a liquid-cooled engine provided with a crankcase that supports a crankshaft so that the crankshaft can be rotated, a cylinder barrel having a cylinder bore and a water jacket on the cylinder side for cooling. The water jacket encircles the cylinder bore and is connected to the crankcase. A cylinder head includes a water jacket on the head side communicating with the water jacket on the cylinder side and is connected to the cylinder barrel.
2. Description of Background Art
A liquid-cooled engine is disclosed in JP-A-2002-213302. In the conventional type liquid-cooled engine, the cylinder barrel and the cylinder head are separately formed. The work necessary for connecting the cylinder barrel and the cylinder head to the crankcase is troublesome. In addition, to maintain the sealing performance of a gasket inserted between the cylinder barrel and the cylinder head, a bolt for fastening the cylinder barrel and the cylinder head is required, the number of parts increases, and the weight of the engine increases.
The present invention is made in view of situation discussed above. It is an object of the present invention to provide a liquid-cooled engine in which the connection of a cylinder barrel and a cylinder head to a crankcase is simplified and which can contribute to a reduction in weight.
To achieve the object, the present invention provides a liquid-cooled engine with a crankcase that supports a crankshaft so that the crankshaft can be rotated. A cylinder barrel includes a cylinder bore and a water jacket on the cylinder side for providing a cooling fluid that encircles the cylinder bore and is connected to the crankcase. A cylinder head includes a water jacket on the head side that communicates with the water jacket on the cylinder side and is connected to the cylinder barrel. A plurality of mounting bosses extend from a fitting plane to the crankcase of the cylinder barrel to the cylinder head and are integrated with a cylinder block in which the water jacket on the cylinder side and the water jacket on the head side mutually communicate. The cylinder barrel and the cylinder head are integrated in a state in which the mounting bosses encircle the cylinder bore and the cylinder block is fastened to the crankcase by bolts inserted into each mounting boss.
The present invention provides a coupling wall for coupling at least one set of the mounting bosses out of the mutually adjacent two sets of a pair of mounting bosses between the cylinder bores mutually adjacent to each other in an axial direction of the crankshaft and being integrated with the cylinder block having the plurality of cylinder bores arranged in the axial direction of the crankshaft.
Further, the present invention provides rod guide pipes wherein each rod to which power from the crankshaft is transmitted and which configures a part of a valve system is inserted so that the rod can be axially moved and the coupling wall are arranged on sides of both cylinder blocks.
According to the present invention, as the cylinder block is composed of the cylinder barrel and the cylinder head which are integrated and the cylinder block is fastened to the crankcase, the connection of the cylinder barrel and the cylinder head to the crankcase can be simplified. No gasket is required to be positioned between the cylinder barrel and the cylinder head. No bolt for is required for maintaining the sealing performance of the gasket. The number of parts may be reduced. Thus, the weight of the engine can be reduced. In addition, the circumferences of the cylinder bore can be sufficiently reinforced by the plurality of mounting bosses encircling the cylinder bore so that a fastening load of the bolts inserted into the mounting bosses can be born.
According to the present invention, no bolt is required to be arranged between each cylinder bore. Thus, the strength of the cylinder barrel between the cylinder bores can be increased by the coupling wall, distance between the cylinder bores in the axial direction of the crankshaft can be reduced, and the engine can be miniaturized.
Further, according to the present invention, the balance in rigidity between the cylinder blocks is enhanced and the occurrence of distortion relative to the inside diameter of the cylinder bore with which the cylinder block is provided can be inhibited.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.